The objective of the proposed research is to characterize tumor-associated antigens of human colonic tumors. Of particular interest is the carcinoembryonic antigen (CEA) described by Gold and Freedman. CEA will be extracted from two human colonic tumors which have been xenografted to hamsters and which also are growing continuously in cell culture. Methods to be employed in purification will include column chromatography, electrophoresis, and equilibrium centrifugation in a CsC1 gradient. A radioimmunoassay will be used to assay CEA during these procedures. Immunological characterization of CEA will use techniques of immunodiffusion and immunoelectrophoresis. In vitro studies will be undertaken to study aspects of CEA, mucin, blood group antigens, and cell surface glycoprotein biosynthesis in relation to the cell cycle. Cells will be pulse-labeled with various radioactive precursors to study these different parameters. The tumor-bearing hamsters will be examined for cell-mediated and humoral antibody responses to the tumor. Of particular interest is whether anti-CEA antibodies are cytotoxic to colonic tumor cells and whether CEA will elicit a delayed-type hypersensitivity response in tumor-bearing hamsters. A radioimmunoassay will be used to detect anti-CEA antibodies, and cell-mediated responses will be measured by lymphocyte transformation, MIF, and skin reactivity tests.